Proteomic quantification of HER-2 abundance and activation in pancreatic ductal adenocarcinoma tumor specimens using reverse phase protein array.
Authors: Jamie Randall, Timothy Lewis Cannon, Allison L Hunt, Aratara Nutcharoen, Laura Johnston, Hongkun Wang, Raymond Couric Wadlow, Arthur Winer, Jasmine Huynh, Nicholas W. Bateman, Justin B Davis, Brian Corgiat, Emanuel Petricoin, Thomas P. Conrads
Journal: Journal of Clinical Oncology (2023)

e16299 Background: Pancreatic adenocarcinoma (PDAC) is associated with poor survival and low response rates to available therapies, warranting a critical need for new treatment paradigms. Enrichment of tumor epithelium via laser microdissection (LMD) prior to reverse phase protein array (RPPA) analysis allows for the quantitative measurement and functional assessment of the activation state of protein drug targets. As part of an IRB-approved Molecular Tumor Board study at Inova Schar Cancer Institute, we harvested enriched tumor epithelium using LMD to support CLIA-based RPPA analysis of patients with pancreatic, breast, and other solid tumor malignancies to examine quantitative expression and activation (phosphorylation) of HER-2/3 and other known cancer-related pathways. Methods: Formalin fixed paraffin embedded (FFPE) primary and/or metastatic tumor biopsy specimens were obtained from 14 patients with PDAC, 14 patients with breast cancer, and 40 patients with other solid tumor malignancies. Tumor epithelium (5-10 µm 2 ) was enriched via LMD prior to RPPA analysis for quantification of HER-2 Total and phosphorylated (p)HER-2 Y1248 and (p)HER-3 Y1289 abundances as part of a 32-marker, CLIA-based RPPA panel examining the total and phosphoprotein abundances of targets with known relevance in solid tumors. Next generation sequencing (NGS; DNA-seq and RNA-seq) was performed on remaining tissue from each specimen. Fisher’s Exact test was used to compare activated HER2 Total , pHER2 Y1248 and pHER3 Y1289 . Results: RPPA analysis of LMD enriched tumor samples revealed significant HER-2 Total expression in patients with PDAC vs other solid tumors (p=0.0112), with HER-2 Total levels comparable to those measured in patients with breast cancer (p=0.0962). The mean HER-2 Total abundances in PDAC, breast, and all other solid tumor malignancies were 1.6, 1.3, and 0.9, respectively. Activated pHER-2 Y1248 and pHER-3 Y1289 abundances did not differ between patients with PDAC vs all other solid tumors or between patients with PDAC vs breast cancer (p&gt;0.05). RNA-seq analysis revealed ERBB2 overexpression in four of the 14 PDAC patients, while ERBB2 amplification by DNA-seq was not observed in any of the PDAC cases. Conclusions: HER-2 expression is not routinely evaluated in clinical practice in PDAC, but our results show higher median expression in PDAC than our solid tumor cohort, with nearly 50% of PDAC cases having total HER2 expression of 2+ or above. Our results may have clinical implications, especially as new classes of HER2 antibody drug conjugates are considered for patients with HER2 non amplified tumors across organ sites, and justify further investigation in a larger cohort. Clinical trial information: U20-11-4308 . [Table: see text]